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Asbestos Rubber Sheets — Oil & Chemical Resistance Explained
(Also known as asbestos gasket sheets, oil-resistant asbestos rubber sheets, and asbestos-reinforced rubber sheets.)
Short conclusion — don’t treat “oil-resistant” as “resistant to everything”.
Asbestos rubber sheets that are labeled “oil-resistant” perform well in many hydrocarbon services, but they are not invulnerable. Before you specify or buy, always confirm three things: the oil type, the maximum operating temperature, and whether water or aggressive chemicals will be present. Don’t decide based only on a label.
Base polymer (rubber type). Nitrile rubber (NBR) content is the most important factor. Sheets with 35% NBR or more may be marketed as “oil resistant.” Products with less than 30% NBR are generally suitable for only short-term oil contact. Our standard Aohong formulation uses 40% NBR. In our tests, ASTM No. 3 oil at 100 °C for 70 hours produced a volume swell of ≤ 8%, which is well below the 12% national limit.
Asbestos fiber grade. Short-fiber Canadian asbestos (CF-4) offers superior mechanical retention after oil exposure — tensile strength retention typically remains above 85% after oil soak. Long-fiber grades (for example, some South African fiber) are cheaper but tend to absorb more oil (roughly 10–20% higher absorption) and show a greater tendency to blister.
Curing / crosslinking system. A peroxide cure with an appropriate secondary cure (for example, lead oxide with dicumyl peroxide) generally yields a denser crosslinked network that resists oil ingress. Conventional sulfur cures produce shorter crosslinks that soften under prolonged hot-oil exposure.
| Oil type | Temp | Soak time | Thickness swell | Weight gain | Surface condition |
|---|---|---|---|---|---|
| Diesel (No.0) | 70 °C | 168 h | +2.1% | +1.8% | No blistering |
| Gasoline (92#) | 23 °C | 168 h | +12% | +9.5% | Sticky at edges |
| SAE 15W-40 engine oil | 100 °C | 168 h | +3.4% | +2.9% | Slight hardening |
| Transformer oil | 80 °C | 168 h | +1.9% | +1.5% | No change |
| Aviation kerosene | 60 °C | 168 h | +8.7% | +6.2% | Surface fuzzing |
Interpretation: high-aromatic fuels such as gasoline and kerosene produce the most swelling. Diesel, typical engine oils, and transformer oil are generally compatible with properly formulated NBR-based asbestos rubber sheets.
Strong alkalies (pH > 11): Alkaline solutions hydrolyze asbestos fibers and quickly reduce mechanical strength. In aggressive alkaline wash service the fiber content can leach out and tensile strength may drop dramatically within weeks. For alkaline service use non-asbestos aramid fiber sheets.
Strong acids (for example, 10% H₂SO₄ or 5% HCl): NBR is not acid resistant. Surface degradation can appear within 24 hours at ambient temperature. In acidic environments choose a fluoroelastomer (FKM) non-asbestos sheet.
Ethylene glycol antifreeze: Extended exposure at high temperature (100 °C, 168 hours) can harden the sheet and reduce compression recovery to unacceptable levels. Remedy: increase NBR content to ~50% or use a non-asbestos alternative.
Refrigerants (R134a): R134a vapor at ambient temperature is usually acceptable, but at elevated temperatures decomposition products can form corrosive fluorine species that attack the asbestos-rubber interface. For hot refrigerant exposure prefer FKM sheets.
A refinery in Shandong experienced catastrophic gasket failure in 2023 after installing an “oil-resistant” asbestos sheet in an alkaline vacuum wash area (pH ~13, up to 90 °C). Within two months gaskets disintegrated, and approximately 38% of the asbestos fiber content leached from the sheets. The plant replaced asbestos gaskets with FKM and aramid non-asbestos sheets and stopped the leaks. Lesson: never use asbestos sheets where strong alkali and elevated temperature coexist.
Diesel, engine oil ≤ 100 °C — Asbestos rubber sheet, NBR 40% recommended.
Gasoline, kerosene ≤ 60 °C — Short-term use ok; for long-term service choose aramid non-asbestos.
Alkaline water (pH > 11) — Do not use asbestos; use aramid fiber sheets.
Strong acids — Do not use asbestos; use FKM non-asbestos sheets.
Ethylene glycol at high temperature — Increase NBR to 50% or switch to non-asbestos.
Refrigerants — Ambient vapor OK; for hot exposure use FKM.
Always confirm three items before ordering: the oil type, the maximum temperature, and whether water or aggressive chemicals are present. If any answer indicates temperature above 100 °C, strong alkali, or strong acid, choose a non-asbestos or FKM solution. Our warehouse stocks NBR-40% and NBR-50% grades, thickness range 0.5–5.0 mm, with same-day slitting and die cutting. Emergency orders ship in three days.
Final reminder: Ask about oil type, temperature, and moisture first. The cost of a single shutdown usually far exceeds the price difference between asbestos and non-asbestos alternatives.
